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1940 Plymouth running funny


Rodney Bullock

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Hi all, I have been playing with my Plymouth here lately and The car is doing something strange. When I put it in 1st gear it bucks like a horse that has not been broken in. I can't seem to stop it. I have given it a tune up I replaced my points with the new electronic ignition and it does the same thing. has anyone had this problem before, it seems I did have this problem a long time ago however I don't remember (old) what I did to fix it. Any thoughts? I think it's the carb What do I know.

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More information would help.  Idling in neutral? Just changed the points to electronic or was more involved ( what other parts?) Does it do it throughout the rpm range or just at idle?  How long has it been doing this and did it start all at once or gradually get worse.  What have you tried and did any of it make it better or worse?

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Check for proper volume of fuel from the pump.  Years ago I had a problem with a /6 car, but at higher rpm in second gear.  If I ran it up to high rpm before shifting to third, the pump couldn't keep up with enough gas and it would buck like crazy,let off or shift to high and every thing was fine.  

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12 hours ago, Rodney Bullock said:

The Bucking occurs when you are pulling out in first gear and a little in second gear. Only when the car is driving. At idle the car runs perfect.

Does your clutch work smoothly? Can you get the car to start out smoothly if you feather the clutch differently than you used to?

I had a friend try out my Dodge and he was not used to the sweet spot on the clutch and he popped the clutch and the car bucked like crazy.

I figure the universal joint has some play in it, but if you let out the clutch smoothly the transfer of power to the differential works fine.

Has your Plymouth been sitting for awhile? Has the universal been lubed and inspected for excessive play?

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I would have a look in the distributor but first, disconnect the vacuum advance line at the carburetor then drive the car.  If the bucking goes away or changes  then the problem lies in the flexible leads in the distributor which insure a good ground to the points plate (moveable) and to the coil connection.

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The clutch is fine. I do remember this happening before and It had something to do with the fuel pump. I think the bowl was very dirty and I emptied it and filled it. The problem then went away. I have a cap and rotor coming in the mail. When I rev the motor it back fires out the exhaust a little. that tells me it's ignition related. I think. We will soon see.  

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This might sound strange, but is your emergency brake adjusted correctly?

I had a problem with my car bucking, mostly in reverse when backing out of the garage.

It turned out to be the shoes on the e brake needed adjusting.

 

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I'm experiencing the same thing.  Lets me get going down the road and within moments it bucks under load.  I have done everything possible on the electrical side and fuel delivery, and have narrowed it down to the fuel pump.  I will let you know what I find.

 

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Hi, Did ever clean the bowl on your fuel pump. The screen on it. I am also waiting for my Cap and rotor from Burnbaum. I was driving the car the other day and It did the bucking just a little. I also check the timing. I have it 4 degress before TDC.I had a guy come over the other day, he said that the choke flap in the Carb needs to be slanted and not straight up and down.

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Uh, no, the engine is supposed to run fine when warmed up with the flap straight up and down.  If it runs better with the flap slanted, I'd be looking for some kind of vacuum leak

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 Hi all, so the cap and rotor came in and I installed them. The car ran better however it just cut off after running for a while. I then removed the bowl at the fuel pump. There was some stuff in the bottom. I cleaned it and then took the top off the carb. There was a lot of stuff in the bottom of the carb. I cleaned all of it out and reassembled it. I started the car and it ran ok. I think I need a new carb so I ordered one from Mr. Isgro. I also ordered a fuel pump to be on the safe side. I have replaced nearly everything.  I think it's a fuel problem.  

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1 hour ago, Rodney Bullock said:

 Hi all, so the cap and rotor came in and I installed them. The car ran better however it just cut off after running for a while. I then removed the bowl at the fuel pump. There was some stuff in the bottom. I cleaned it and then took the top off the carb. There was a lot of stuff in the bottom of the carb. I cleaned all of it out and reassembled it. I started the car and it ran ok. I think I need a new carb so I ordered one from Mr. Isgro. I also ordered a fuel pump to be on the safe side. I have replaced nearly everything.  I think it's a fuel problem.  

In the interim, how about 2 inline fuel filters, 1 frm the fuel pump to carb, and 1 from the tank before the pump. This might keep things clear until you decide what to do, you either have crud in the tank or the fuel lines.

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The stuff is likely a result of ethanol fuel.  If you let vehicles sit for more than three weeks or so the build up of crud starts where the fuel sits and evaporates.  A fuel stabilizer can help, keeping fuel fresh can help, and of course finding and using non ethanol gas works too. With a fleet of vehicles like yours a regular schedule of driving them will keep the healthy as well.

 

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Hi all, My gas tank was done by a company called Re-nuz-it many years ago. I have a filter at the rear wheel and I am planning to install another at the carb. I was playing with the car today and after a vision last night I checked the wiper vacuum line at the manifold and found the line very loose this is why it was running funny, vacuum leak. I also advanced the timing just a little. I have not driven the car. I am going to install the fuel pump as I think the crud I found in the carb has to be in that pump. Let's cross our fingers and toes. Cleaning that tank has crossed my mind. I might do it over the boring winter months. Hey Greg, I solved the problem of stale gas when I can't drive them I run them out of gas. The only car I must drive one more time is the 1966 Pontiac 2+2 convertible, That thing is exciting! 

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I have been using the new Stabilizer 360 product in my 39 Desoto.  This addative creates a vapor to coat the upper part of the gas tank metal that is not currently being covered with the gasoline and it is also a stabilizer.  You can get the product at Walmart and they have the best price.  Best to put this in you tank when it is going to sit for a while and will last and protect the car for 12 months if the car sits over the winter.

 

They recommend to put this in everytime you fill up the tank and it also acts as a line cleaner and carb cleanrer.  Good protection for only a few dollars especially with these old metal gas tanks and metal fuel lines and FP and old carbs.

 

Rich Hartung

Desoto1939@aol.com

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